The anthraquinone-hydroquinone process for preparing hydrogen peroxide is well known and widely used. In this process, an alkylanthraquinone is catalytically hydrogenated to the corresponding hydroquinone, which is then oxidized to regenerate the anthraquinone and simultaneously produce hydrogen peroxide.
Palladium on a silica support is a good catalyst for that process because of the low surface activity of silica, although there have been reports of early failures of this type of catalyst due to the palladium not adhering to its support as well as it should.
Copelin, in his U.S. Pat. No. 4,240,933, discloses a palladium-on-silica catalyst in which adhesion of the palladium to its silica support is enhanced by incorporating into the catalyst a compound of zirconium, thorium, hafnium, cerium, titanium or aluminum.
It has now been found that a Copelin type of catalyst can itself be improved with respect to adhesion of the palladium to its support if the catalyst is prepared by the process of this invention. The catalysts thus produced also have excellent filterability.